Tackling Particle Morphology in the Micromechanical Study of Crushable Sands: A Combined Experimental, Theoretical and Numerical Approach

Description

Among many kinds of uncertainties that affect the design and construction ofgeotechnical infrastructures in sand, the incomplete understanding of particle breakagebehavior and its effect on the macro-mechanical properties of sand constitutes a majorsource of uncertainty. This has caused engineering failures of driven piles and largescalerock-fill dams in China and other countries around the world in the past fewdecades. Concerning the fundamentals of the breakage mechanics, particle morphology iswell known to play an important role in the sand crushing behavior. To date, however,very little is known about the intrinsic relationship between particle breakage andparticle morphology evolution, and their influences on the macroscopic properties ofsands.In view of the above deficiency, we propose an advanced investigation into the sandparticle morphology and its influence on the particle breakage behavior and themacroscopic shear strength of sands using a combined experimental, theoretical andnumerical approach. Specifically, the experimental investigation involves the use ofnanofocus X-ray computed tomography (CT) in the visualization and characterization ofsand particle morphologies and their evolution during the triaxial loading process. Thenthe theoretical investigation employs the spherical harmonics analysis (SHA) for thereconstruction of real sand particle morphologies acquired from the CT study andimplement it in the 3D discrete element method (DEM) modeling of real sands. Finally,the numerical investigation establishes a probability-based DEM modeling approach forthe realistic simulation of particle breakage and fragmentation behaviors.This innovative research will unravel the intrinsic linkage between particle morphologyand particle breakage, and their relationship to the macroscopic shear strength of sandsunder the triaxial shearing condition. A novel probability-based DEM simulation methodwhich can incorporate both actual sand particle morphologies and realistic particlebreakage behavior will also be created. This will expedite the uptake of DEM in thegeotechnical industry.The outcome of this research will produce both scientific and engineering impacts. Theformer comes from an improved understanding of the fundamentals of micromorphologyand micromechanics of crushable sands and its possible contribution to the research onother related breakable granular materials. The latter is mainly reflected in theenhanced ability of engineers to make improved design and construction of geotechnicalsystems in crushable soils. This is very relevant in Hong Kong where highly decomposedgranite or volcanic soils exhibit distinct breakage characteristics.?